|  | 5.3 | IP Routing Protocols
| 5.3.3 | Routing loops
The Figure shows a routing loop. In this case, a packet arrives at Router 1 at Time T1. Router 1 has already been updated and knows that the best route to the destination calls for Router 2 to be the next stop. Router 1 therefore forwards the packet to Router 2. Router 2 has not yet been updated and believes that the best next hop is Router 1. Therefore, Router 2 forwards the packet back to Router 1. The packet will continue to bounce back and forth between the two routers until Router 2 receives its routing update or until the packet has been switched the maximum number of times allowed. Different routing protocols have different maximums; the network administrator usually can define lower maximums. For example, IGRP has a maximum hop count of 255, it defaults to 100, and it is usually set to 50 or less.